long append="..." causes yaboot to reject entire yaboot.conf (MAX_TOKEN too small)

long append="..." causes yaboot to reject entire yaboot.conf (MAX_TOKEN too small)

yaboot's second/cfg.c has:
  #define MAX_TOKEN 200

When yaboot parses its config file, if it encounters a quoted string (like
append="...") longer than MAX_TOKEN, it rejects the entire config.

Typical preupgrade usage uses ~250 chars, which means preupgrade currently
renders ppc systems unbootable without this patch.

Suggest increasing MAX_TOKEN to.. let's say 511. cfg.c does "char
buf[MAX_TOKEN+1]", and everyone loves powers of 2.

Signed-off-by: Roman Rakus <rrakus@redhat.com>
Signed-off-by: Tony Breeds <tony@bakeyournoodle.com>